|
|
In this exhibit you learn about how infrared allows us to see heat.
Heat can travel in three different ways: conduction, convection and radiation. Conduction mostly occurs in solids, convection in liquids and gases, and radiation can move through anything, even a vacuum.
Warmth causes particles to move more. In a solid this means they are vibrating in one place. As they vibrate, they whack against other particles, causing them to move too. This movement warms them up, and they move even more. This causes them to whack against more particles, and warm them up too. Soon the particles will all be warm and vibrating. This is conduction.
Convection occurs in liquids and gases. In liquids and gases the particles are already moving: in liquids they're slipping and sliding past each other and in gases they're zooming around the space. Because of the way the particles are moving around, any particles you heat up will move to another place. The warm particles will be spread throughout the space and warm it up.
All warm things also give out infrared radiation. A solid conducting heat and a liquid convecting heat will give out infrared radiation. Infrared is a wave, much like light, radiowaves and X-rays. Warm objects give out infrared and it can be absorbed by other objects.
We can't see infrared, but we use special cameras to show it. They are often called thermal imaging cameras because they allow us to see how warm things are. Thermal imaging cameras have lots of uses, such as viewing weather systems, analysing chemicals and analysing the layers of old paintings. But the most common use of thermal imaging cameras is to look at animals (including humans).
Animals are warm and give out a lot of infrared radiation. Infrared can therefore be used to watch people and animals in different situations. For example, the military use it to find the enemy, the police to chase criminals and the fire service to find casualties. Infrared cameras are also used to study nature, to watch animals' behaviour by night.
|
Questions
|
| 1 |
Heat can travel in ________ ways. |
| 2 |
What do particles do when they are warm? |
| 3 |
How do particles move in a gas? |
| 4 |
What is infrared? |
| 5 |
What do we most commonly look at using infrared cameras? |
| 6 |
Some animals can see infrared: why do you think this would be useful? |
|
Activities
|
| 1 |
If you have a smartphone, you can download infrared camera apps (try to find a free one). Use an infrared camera app to take pictures of people and animals. Take a picture of a remote control pointing at the camera with a button pressed down. What do you see? |
| 2 |
Watch convection in water. Fill a bowl with water and drop a single drop of food colouring into the water. Watch it spread out. Try it with a bowl of warm water and a bowl of cold water. Is there a difference? Why do you think that is? |
|
